Single-tube and double-tube optical glass.



H. FOUASSE.

SINGLE TUBE AND DOUBLE TUBE OPTICAL GLASS.

2 SHEET/SHEET I.

Patented Apr. 29, 1919.

APPHCATION FILED MAR- 23,1913- H. FOUASSE.

SINGLE TUBE AND DOUBLE TUBE OPTICAL GLASS.

APPLICATION FILED MAR. 23. 1918.

Patented Apr. 29,1919.

2 SHEET$SHEET 2.

UNITED STATES PATENT OFFICE.

HENRI FOUASSE, OF PARIS, FRANCE; ASSIGNOR- TO SOCIETE DZOPTIQUE ET DEMECANIQUE DE HAUTE PRECISION, 0F PARIS, FRANCE, A JOINT-STOCK COM- PANYOF FRANCE.

Specification of Letters Patent.

Patented Apr. 29, 1919.

Application filed March 23, 1918, Serial No. 224,360.

T 0 all whom it may concern Be it known that I, HENRI FoUAssn, a c1t1-zen of the French Republic, and a resident of 125 Boulevard Davout,Paris, France, have invented a new and useful Improvement in Single Tubeand Double Tube Optical Glasses, which invention is fully set forth inthe following specification.

The present invention relates to an 1m provement in optical prismaticapparatus, such as single and double tube optical glasses, which givesto the instruments a wide field of view while permitting them to be ofs1zes of small dimensions.

The improvement consists essentially in placing the objective betweenthe erecting prisms.

The present invention is characterized, moreover, by a specialcombination of erecting prisms which permits their dimenslons beingreduced and in consequence the size of the instrument.

In the accompanying drawing:

Figure 1 shows diagrammatically the ordinary arrangement of prisms ofsingle and double tube optical glasses;

Fig. 2 represents similarly the improved optical arrangement accordingto the present invention.

Figs. 3, 4L and 5 show respectively in elevation, in plan and in endview an optical train embodying the improved optical arrangement.

Figs. 6 and 7 represent in horizontal section and vertical section adouble tube optical glass having a wide base arranged according to theinvention.

In single and double tube optical glasses in which the image is erectedby means of prisms disposed according to ordinary arrangements, theangle of the real field of view '10 is limited, as shown in Fig. 1, bythe fact that the length of the luminous pencil, emanating from theobjective at and traversing the system of ercctin prisms b 0 1s verygreat, about four times t e width of the exit face of the latter prism.This arrangement presents no inconvenience in instruments of strongmagnifying power where the angle of the real field of View is limited bythe value of the apparent field of view to which the high magnificationgives rise.

In instruments with small magnifying power, on the contrary, the fieldof View is always necessarily reduced, for, if in order to obtain alarger field the dimensions of the prisms are increased, the instrumentis not only bulky but its construction would be unrealiaable by reasonof the formation of the image inthe interior of these prisms.

The improvement, the object of the present invention, consists inplacing the objective 0. between the two prisms b and c as shown in Fig.2.

In this arrangement of the objective a, the field of view angle w ismuch greater than in the case of the ordinary arrangement shown in Fig.l, where the objective is placed in front of the first erecting prism b.

The improved optical arrangement can be applied to different forms ofsingle and double tube optical glasses.

Figs. 3 to 5 show an optical train in which the obpective a is placedbetween two doubly reflecting erecting prisms b a of the Crova type.

In this arrangement, the image, which is formed in the plane XX, is, byreason of the large field view which the instrument gives, greater thanthe erecting prisms, and is produced at a distance from these lattersuflicient to permit the employment of lenses of considerable convergingcharacter for the eye piece (1 as shown in Figs. 3 and 4.

Figs. 6 and 7 represent a double tube glass with a wide base, comprisingthe optical arrangement described above and also a special combinationof erectin prisms which allows of a reduction in the dimensions of theselatter and consequently in the size of the instrument.

In this glass each objective (in is placed between a doubly reflectingprism b of the Crova type, by which the luminous rays enter, and asimple total reflecting prism 0; another similar prism 0 effects theerection of the image and reflects the luminous penoil into thecorresponding eye piece (Z these two total reflecting prisms c, 0 areorientated or disposed, respectively, in such a manner that theirreflecting surfaces cause the erection. of the image in the same manneras a Crova prism.

This arrangement permits dimensions being given to prisms b, 0corresponding to the diameter of the objective a, and consequentlygreatly reduced dimensions when the instrument is required only to givea small mag nification; the last prism 0 only should be suflicientlylarge to receive or include the image.

Double tube glasses. can thus be made to have a wide field of view, andany base regulated by the separation of the two prisms 0, 0

The described arrangement can be applied especially to the constructionof glasses for use at sea and in theaters, which glasses would have theadvantage over ordinary prismatic glasses of having a wide field of Viewand great clearness, while at the same time would be of small bulk.

It will be understood that the details of construction for applying theimproved optical arrangement can be modified to suit differentinstruments.

Having thus fully described the nature of the said invention and thebest means we know of carrying the same into practical effect, I claimIna. double tube optical glass with wide base, the combination in eachtube of an optical train comprising an objective, a doubly reflectingprism of the Crova type on one side of the objective, and a simple totalreflecting prism on the other side of the obj ective, with a simpletotal reflecting prism and an eye piece, said last-named prisms being sodisposed that the reflecting surfaces thereof cause an erection of theimage similarly to a Crova prism and reflect the luminous pencil to theeye-piece.

In testimony whereof I have signed this specification.

HENRI FOUASSE. Witnesses:

HENRI MONIN,

MARCEL GUILLEMOT.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. 0.

